1. Field of the Invention
This invention relates to automatic mechanical transmission systems and in particular to automatic mechanical transmission systems comprising a compound change gear transmission of the type comprising a multi-speed main transmission section connected in series with a multi-speed splitter type auxiliary transmission section wherein the main transmission section utilizes nonsynchronized, unblocked resiliently shifted jaw clutch assemblies to selectively engage a selected main section ratio and wherein the auxiliary section utilizes blocked resiliently shifted jaw clutch assemblies to selectively engage a selected auxiliary section ratio and a control system therefor. Preferably, the blockers and associated clutch members in the auxiliary transmission section have complementary ramps on the blocking members thereof configured to prevent nonsynchronized engagement of the associated jaw clutch members when the main section is engaged but which will tend to act as positioners to place the associated blocker and clutch member in a nonblocking condition when the main section is in a neutral or disengaged condition. Preferably, the transmission is driven by a throttle control engine and the control system includes a central processing unit for receiving input signals indicative of at least engine speed and throttle position, for selecting a desired gear ratio in accordance with a predetermined program acted upon by current and/or stored input information and for generating command signals to a transmission operating mechanism.
2. Related Application
This application is related to my copending U.S. patent application Ser. No. 287,470, filed July 27, 1981, and titled Semi-Blocked Transmission.
3. Description of the Prior Art
Compound transmissions of the splitter or range type or a combination thereof, are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,105,395; 3,648,546; 3,799,002; 2,932,988 and 3,229,551, all hereby incorporated by reference.
Blocked change gear transmissions of both the single and compound types are also well known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,799,002; 3,921,469; 3,924,484; 3,983,979; 4,192,196 and 4,194,410, all of which are hereby incorporated by reference.
Control systems for automatic mechanical transmissions are known in the prior art as may be seen by reference to Published British Patent Application No. 2,012,892 which corresponds to allowed U.S. patent application Ser. No. 190,512 filed Jan. 24, 1978 now U.S. Pat. No. 4,361,060, hereby incorporated by reference.
In the design of transmissions, particularly heavy duty constant mesh mechanical transmissions, such as used in heavy duty trucks, there has existed for a long time the problem of shifting the transmission to the various speed ratios, which problem is even greater when the transmission is compounded, that is provided with an auxiliary transmission section of the range or splitter type for increasing the number of speed ratios. Most previously known compound mechanical transmissions have required a relatively high level of operator skill or necessarily utilized synchronizers, of which many different types are known, for causing the speed of the jaw or tooth clutch members to be substantially synchronized prior to permitting their interengagement during a shifting sequence from one speed ratio to another speed ratio. While the use of synchronizers does permit the shifting operation to be performed, their use, as is already known, imposes certain requirements of weight, space and power which is desirable to ease, or avoid entirely, if possible. Compound transmissions utilizing resiliently shifted blocked jaw clutch mechanisms are known in the prior art and have provided a transmission shifting mechanism which eliminates the necessity of synchronizer clutches while providing a transmission which is relatively easier to shift than the nonblocked, nonsychronized mechanical transmissions of the prior art. Automatic control systems for mechanical transmissions which include a central processing unit having a predetermined program or set of logic rules for acting upon certain input signals, such as at least inputs indicative of engine speed and throttle position, to select a desired gear ratio and to generate command output signals to the transmission to command an upshift to a higher gear ratio or a downshift to a lower gear ratio if required are known in the prior art. While such automatic mechanical transmission systems provide a highly desirable and highly efficient automatic transmission, the prior art automatic mechanical transmission systems have not been utilized in connection with automatic mechanical transmissions of the blocked or semi-blocked type and thus have not been operable to command a desired gear ratio change in a sequence taking full advantage of the operational advantages of a blocked or semi-blocked transmission.